The over-all objective was to discover especially susceptible lines of inbred Syrian hamsters which may serve to discover urinary bladder carcinogens and to distinguish such strains from others that might be resistant to strong bladder carcinogens. The objective for the first year is to accumulate sufficient numbers of inbred Syrian hamsters of as many strains as possible to subject them to feeding of 1% beta-naphthylamine or 0.1% o-amino-azotoluene which are both powerful inducers of urinary bladder cancer in certain species.